Pneumatic cylinder assemblies

ABSTRACT

A pneumatic cylinder assembly incorporating hydraulic damping, said assembly comprising a pneumatic cylinder, a pneumatic piston slidable within said cylinder and a pneumatic piston rod operatively connected to said pneumatic piston, and a hydraulic damping cylinder assembly incorporating a hydraulic cylinder arranged within the pneumatic piston rod, a hydraulic piston within said hydraulic cylinder and a hydraulic piston rod operatively connected to said hydraulic piston and secured to an end wall of said pneumatic cylinder remote from said pneumatic piston rod.

United States Patent Weyman [151 3,678,805 [4 51 July 25,1972

1541 PNEUMATIC CYLINDER ASSEMBLIES 72] Inventor: Henry Walter Weyman,Waterworks Road, Worcestershire, England [22] Filed: Oct. 22, 1970 21Appl. No.: 83,098

2,081,921 6/1937 Gartin 92/9 X 3,149,541 9/1964 Hutter et al... ..92/8 X3,146,680 9/1964 Hutter et al ..92/1 11 X 3,313,214 4/1967 Ackerman..92/8

Primary Examiner-Martin P. Schwadron Assistant Examiner-Leslie T. PayneAttorney-Kenway, Jenney & Hildreth 5 7] ABSTRACT A pneumatic cylinderassembly incorporating hydraulic damping. said assembly comprising apneumatic cylinder, a pneumatic piston slidable within said cylinder anda pneumatic piston rod operatively connected to said pneumatic piston,and a hydraulic damping cylinder assembly incorporating a hydrauliccylinder arranged within the pneumatic piston rod, a hydraulic pistonwithin said hydraulic cylinder and a hydraulic piston rod operativelyconnected to said hydraulic piston and secured to an end wall of saidpneumatic cylinder remote from said pneumatic piston rod.

3 Claims, 1 Drawing Figure BACKGROUND Throughout the specificationreference is made to both pneumatically operable cylinder assemblies andto hydraulically operable cylinder assemblies and throughout thespecification the words pneumatic" and hydraulic used in relation topiston, cylinder, piston rod" or cylinder assembly is intended to referto such a device which is operable pneumatically or hydraulicallyrespectively.

A disadvantage of pneumatic cylinder assemblies in some applicationsarises due to the compressibility of the air which is used as apneumatic medium. When the cylinder assembly is subjected to pressure,the initial movement of the cylinder is relatively slow because it takessome time for pressure to build up. However, once a substantial pressurehas built up the cylinder assembly moves at an uncontrolled high speed.It is not possible to exert substantial control on the movement bythrottling the air because this slows the initial response of thecylinder.

Where it is desired to operate a pneumatic cylinder at a relatively slowcontrolled rate this has previously been done by providing a hydrauliccylinder assembly to damp the movement of the pneumatic cylinder andthereby prevent a high speed being achieved even when a high pressureand a virtually uncontrolled air supply is used. In known installationssuch a hydraulic damping cylinder assembly is normally mounted alongsideand parallel to the pneumatic cylinder assembly and this has thedisadvantage of occupying a substantial space and of resulting inbending loads due to the off-set line of action of the damping force.

OBJECTS OF THE INVENTION provide an improved SUMMARY OF THE INVENTION Inaccordance with the present invention there is provided a pneumaticcylinder assembly including a pneumatic cylinder, pneumatic piston andpneumatic piston rod and a hydraulic damping cylinder assemblyincorporating a hydraulic cylinder arranged within the pneumatic pistonrod.

Preferably the piston rod of the hydraulic damping cylinder assembly isfixed at one end to the end wall of the pneumatic cylinder remote fromthe pneumatic piston rod.

Preferably there is a hydraulic connection between one side and theother of the hydraulic piston by way of a first bore in the hydraulicpiston rod, a control valve assembly adjacent the end of the hydraulicpiston rod which is secured in the end of the pneumatic cylinder and afurther bore in the hydraulic piston rod leading to the opposed side ofthe hydraulic piston. In this way a hydraulic damping cylinder assemblywithin the piston rod of the pneumatic cylinder assembly can becontrolled so that its degree of damping can be adjusted to a suitablelevel without difficulty.

In some applications where hydraulic damping is required in onedirection of operation only the hydraulic piston may be provided with anon-retum valve which pennits free flow of hydraulic fluid through thepiston in one direction.

In order to compensate for volume changes within the hydraulic cylinderassembly due to relative movement of the piston rod out of the cylinderthe hydraulic cylinder may be provided with a spring operated volumecompensating piston at the end thereof remote from the hydraulic pistonrod.

2 BRIEF DESCRIPTION OF THE DRAWING The attached drawing, forming parthereof is a diagrammatic cross-sectional view through a pneumaticcylinder assembly according to the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT A pneumatic cylinder 11 has apiston 12 which slides within the cylinder 11 and is sealed by means oftwo seals 13 and 14. The piston 12 is carried on a piston rod 15 whichslides in a bore 16 of an end closure member 17 of the cylinder. A seal18 seals the piston rod 15 within the bore 16.

The end of the cylinder 11 opposite the end closure member 17 is closedofi' by a further end closure 19 which for the purpose of the pneumaticoperation effectively completely closes and seals the appropriate end ofthe cylinder. Air supplies for the pneumatic operation of the cylinderassembly are shown diagrammatically at 21 and 22. As thus far describedthe pneumatic cylinder assembly operates conventionally in that supplyof air under pressure to connection 21 while connection 22 is exhaustedcauses the cylinder assembly to expand while a reversal of the airpressure connections causes the cylinder assembly to retract towards theposition shown.

A hydraulic damping cylinder assembly is provided within the cylinder 11in such a way that the hydraulic cylinder 31 is formed within thepneumatic piston rod 15. The hydraulic piston rod carries a hydraulicpiston 33 which slides within the cylinder 31 and is sealed in thecylinder by means of a seal 34. A series of passages 35 extend axiallythrough the piston 33 from one side thereof to the other. A one-wayvalve constituted by a plate 36 held against the ends of the passages 35by a spring 37 prevents flow of hydraulic fluid through the passages 35in a direction from the right to the left as shown in the drawing, butpermits flow in the opposite direction against a relatively small backpressure.

The right hand of the hydraulic cylinder as shown in the drawing isclosed by the pneumatic piston 12 which is threaded onto the piston rod15 and is sealed by means of an O-ring seal 38. A central axial bore 39through the piston 12 forms a passage through which the hydraulic pistonrod 32 passes. The piston rod 32 is sealed within the bore 39 by a pairof seals 41 and 42.

The hydraulic piston rod 32 extends through the pneumatic cylinder endclosure 19 and is secured to this end closure by means of a spigot 43 atthe inner side of the end closure 19 and a nut 44 to the outside of theend closure 19. A pair of O-ring seals 45 seal the piston rod 32 withinthe end closure 19.

A pair of hydraulic fluid bores 47 and 48 run the major part of thelength of the hydraulic piston rod 32 and provide con nections betweenthose parts of the cylinder 31 on opposed sides of the piston 33 by wayof a control valve assembly arranged outside the pneumatic cylinder atthe right hand of the drawing.

The valve assembly incorporates a block 51 which incorporates a manuallyadjustable needle valve 52 with an orifice 53 and a pneumaticallyoperable valve 54 with an orifice 55 (shown closed). Hydraulic fluid inthe cylinder 31 to the right of the piston 33 passes through a crossbore 50, bore 47 and a transverse bore 56 within the block 51 to eitherthe needle valve 52 or the pneumatically operated valve 54. Afterpassing through the valve orifice 53 or 55 fluid then passes by way of acommunicating bore 57 or 58 respectively to an annular groove 59 in theface of the block 51 which bears against the end closure 19. From thisannular groove the fluid passes through two bores 61 and 62 to the bore48 in the piston rod 32. This bore 48 communicates directly with thevolume of fluid within the cylinder 31 to the left of the piston 33.

In order to compensate for changes in overall volume within the cylinder31 due to the movement of the piston rod 32 into and out of the cylinderthe left hand end of the hydraulic cylinder 31 is provided with a springloaded piston 63.

In operation, when the pneumatic connection 21 is pressurized the piston12 and piston rod 15 move towards the left. As the hydraulic piston rod32 is secured to the end member 19 there is also relative movement ofthe hydraulic piston 33 within its cylinder 31. During this movement theone-way valve 36 is closed so that hydraulic fluid passing from one sideto the other of the piston 33 must flow through the bores 47 and 48 andthrough the valve assembly formed within the block 51. If thepneumatically operated valve 54 is closed (as shown) by virtue of airpressure on its piston 64 then the degree of damping provided by thevalve assembly is controlled by the position of the needle valve 52which controls the orifice 53. If it is desired to decrease the degreeof damping this can be achieved by releasing the air pressure suppliedto the pneumatically operated valve 54 and thereby permitting asubstantially faster flow of hydraulic fluid through the completely openorifice 55.

One practical application of the cylinder assembly described above is inthe machine tool industry. There is often a requirement for a relativelyfast approach of a tool to a workpiece or of a workpiece to a toolfollowed by a relatively slow movement while a cutting operation takesplace. An operation of this nature or any other sequence of operationduring which the speed of operation of the pneumatic cylinder assemblyvaries during a stroke can be achieved by operation of the pneumaticallycontrolled valve 54 during the stroke. A fast return stroke is madepossible by virtue of the non return valve 36. However, if it is desiredto control the rate of the return stroke, the non return valve 36 of thepassages 35 in the piston 33 should be omitted.

I claim:

A pneumatic cylinder cylinder assembly comprising:

a pneumatic cylinder;

a pnuematic piston slidable within said pneumatic cylinder;

a pneumatic piston rod operatively connected to said pneumatic piston;

a hydraulic damping cylinder assembly having a hydraulic cylinder,

said hydraulic cylinder lying within said pneumatic piston rod;

two pneumatic connections to said pneumatic cylinder on opposed sides ofsaid pneumatic piston; a hydraulic control valve assembly;

a first hydraulic connection between said valve assembly and thehydraulic cylinder to one side of the hydraulic piston and a secondhydraulic connection between said valve assembly and the hydrauliccylinder to the other side of the hydraulic piston whereby said valveassembly controls the interconnection for fluid flow between said oneside and said other side of the hydraulic piston,

said hydraulic control valve assembly comprising in parallel betweensaid one side and said other side of the hydraulic piston a first valveproviding a restricted inter-connection between said sides and a secondvalve which is selectively closable whereby to force all hydraulic flowfrom said one side to said other side through said restrictedinterconnection and openable to provide free flow between said sides ofthe hydraulic piston.

2. A pneumatic cylinder assembly according to claim 1, said restrictedinter-connection provided by said first valve being adjustable setable.

3. A pneumatic cylinder assembly according to claim 1, furthercomprising a one-way, non-return valve interposed between the hydrauliccylinder to said one side of said hydraulic piston and said hydrauliccylinder to said other side of said hydraulic piston.

" UNITED STATES PATENT OFFICE (5/69) CERTIFICATE OF CORRECTION Patent3,678,805 Dated -Juiy 25,1372 Inveot or (s) a w i Way-went 4 it isoei'tified tha't f i'or '--ap a1hj th'bov'e id enfified patent andthat". said Letters Patenp'ai'e fher'e-by corrected as shown below:

, I v v v 1 'gflo umn' 2., l um 28 should read as E0 ows-.

piston rod 32. c-firries a hydraulic piston 33 which slides. withl fi-hColumn 2 line 37, should read as follows:-

The sight hand end of :he hydraulic cylinder as shown in the Column 2,"Line 53, should read follows:

ranged outs-tide the pneumatic cyiind'er at the right han d end of the,

Column 4-, line 27 should readjas' follows:

adjustabl-y setable.

' Signed and sealed this 2nd day of January 1973.-

EL Attest':

EDWARD M.FLETCHER,JR'. ROBERT GOTTSCHALK Attesting Officer s eCommissioner of Patents

2. A pneumatic cylinder assembly according to claim 1, said restrictedinter-connection provided by said first valve being adjustable setable.3. A pneumatic cylinder assembly according to claim 1, furthercomprising a one-way, non-return valve interposed between the hydrauliccylinder to said one side of said hydraulic piston and said hydrauliccylinder to said other side of said hydraulic piston.